Biosensing instruments have been developed to detect a variety of biomolecular complexes including oligonucleotides, antibody-antigen interactions, hormone-receptor interactions, and enzyme-substrate interactions. In general, biosensors consist of two components: a highly specific recognition element and a transducer that converts the molecular recognition event into a quantifiable signal. Signal transduction has been accomplished by many methods, including fluorescence and interferometry. Biosensing instruments that employ disposable sample strips enjoy wide consumer acceptance. Such instruments are employed for the detection of analytes such as glucose and cholesterol levels in blood samples and, in general, provide accurate readings.
However, to obtain accurate detecting results, the information in association with the disposable strips (such as calibration parameters, strip type and expiration duration, etc.) must be entered in the biosensing instruments. Calibration of the biosensor must be done first before using it. The strips are different lot by lot. The strip manufacturers must provide the calibration code for each lot of strips. The users must perform a set-up procedure before using the strips according to the manufacturers' manual so that the biosensors can receive correct calibration information. There are two setting procedures known in the art for calibration. One is that the user selects a set of built-in calibration codes in the biosensor according to the corresponding calibration codes marked in the package of the strips. The other is that a code card is attached to each lot of strips in order to save the calibration parameters in a memory unit. In a further calibration of the sensor unit, a parameter setting card corresponding to a lot number of a sensor included therein is inserted into the main unit so that the sensitivity of the equipment is calibrated. In a still further calibration of the sensor unit, correction data is supplied to the main unit in accordance with bar codes labelled thereon to calibrate the sensitivity of the biosensing instrument.
U.S. Pat. No. 4,637,403 provides a hand-held shirt-pocket portable medical diagnostic system for checking measurement of blood glucose, urea nitrogen, hemoglobin, blood components or other body qualities. This prior reference describes an integrated system that provides a method by which the patient lances the finger to get a sample of blood which is then used by the device to provide a reading of the blood glucose or other analyte concentration. This system uses a complex reflectance system to read the analyte level in the sample.
European Patent No. 0351891 describes an electrochemical sensor system and electrodes which are suitable for measuring the concentration of an analyte in a body fluid sample. The system requires the use of expensive electrodes and a reader to determine the analyte concentration level.
U.S. Pat. No. 5,053,199 provides a device including an integrated circuit carrier and a socket for removably and longitudinally receiving the integrated circuit carrier. It describes a biosensing meter with a pluggable memory key. This device uses a pluggable memory key to control the operations of the meter.
U.S. Pat. No. 5,366,609 relates to biosensing meters for determining the presence of an analyte in a biological sample, and, more particularly, to a biosensing meter whose operation is controlled by data accessed from a removably pluggable memory module. It describes a biosensing meter with a pluggable read-only memory wherein data read from the read-only memory at sequential times during the use of the meter enables a determination to be made as to whether the read-only memory has been switched during a test procedure.
Although many improvements have been made, the cost and complexity needed for calibration are still significant. The need to match calibration of a meter to the strips leads to errors in analyte concentration readings. Currently, existing calibration mechanisms require loading a calibration chip or strip, or manually inputting a calibration code into the meter. These devices can be reused numerous times, resulting in errors by the patient who does not change to or enter the appropriate calibration data. An additional issue is the use of test strips which are out of date. Old test strips which are expired can lead to errors and inaccurate results. By providing a means to eliminate the use of expired test strips, the patients will not have to monitor the expiration date of the test strips, and patient errors from using old test strips are eliminated.
There remains an important need to develop rapid, simple, cheaper and reliable calibration for biosensing instruments.